Cardiovascular action of verapamil in the dog with particular reference to myocardial contractility and atrioventricular conduction.

Verapamil (Isoptin) caused a dose-dependent peripheral vasodilation, increase in myocardial contractility, and tachycardia in the anaesthetized dog. Propranolol pretreatment blocked the cardiac stimulation following verapamil but the vasodilation was unaltered. Inflation of a thoracic aortic balloon prevented the fall in intravascular pressure and reduced the tachycardia and positive inotropic responses. These experiments suggest that clinical doses of verapamil cause peripheral vasodilation which leads to a sympathetic reflex induced increase in heart rate and myocardial contractility. Verapamil also had a direct myocardial depressant action which became evident at doses above the range used clinically. The drug increased the PR interval in conscious dogs for up to 60 minutes. This effect was partly mediated through cholinergic stimulation and partly through a direct depression on atrioventricular conduction.

Nutritional supplementation and the development of linear enamel hypoplasias in children from Tezonteopan, Mexico.

The purpose of this study was to compare the effect of nutritional intake during tooth-crown formation on the subsequent development of linear enamel hypoplasias (LEHs) in Mexican nonsupplemented (control) adolescents (n = 42) and adolescents who had received daily nutritional supplements since birth (n = 42). The proportion of individuals with LEHs was nearly two-fold greater (74.4%; 95% CI 64.7-84.1%) in the control than in the supplemented group (39.5%; 95% CI 28.6-50.4%; chi 2 = 9.44; P = 0.001). Although the estimated peak age at formation, approximately 2-2.5 y, is similar in both groups, the proportion of early (before 1.5 y) and late (after 3.0 y) LEHs was greater in the control group. LEH was also more common in females and was associated with an increase in illness days and a decrease in growth velocity. Results of this study suggest that mild to moderate undernutrition during enamel formation is causally linked to the formation of LEHs.

Vascular consequences of subclavian artery transection for the treatment of congenital heart disease.

The acute and chronic consequences of subclavian artery transection were analyzed in the noninvasive vascular laboratory. Twenty-eight patients (aged 1 day to 4 2/12 years, median 2 months) underwent subclavian artery transection (23 Blalock-Taussig, four subclavian aortoplasty for coarctation or interrupted arch, and one division of aberrant left subclavian). Bilateral systolic brachial artery pressure (BAP) was measured by Doppler instrumentation to obtain a "BAP index": BAP1 = (operated side BAP/control side BAP). Velocity waveform tracings and bilateral forearm skin temperatures were also obtained during studies before and sequentially after operation (4 hours to 12 years). Five patients underwent exercise testing of the upper extremity. Nine patients were studied for manual preference and limb development. Before operation, mean BAP1 was 0.99. Immediately (4 to 48 hours) after operation, mean BAP1 was 0.39. Three weeks postoperatively, BAP1 was 0.62, and thereafter it remained at 0.70. All differences between preoperative, immediate postoperative and late postoperative BAP1 are significant (p less than 0.001). Exercise resulted in a significant (p less than 0.01) increase in BAP bilaterally. Forearm skin temperature was initially lower (p less than 0.01) on the operated side but approximated the control side by 1 week. Limb girth was less on the operated side (p less than 0.01), without evidence of altered manual preference. In conclusion, subclavian artery transection causes permanent reduction in BAP1. The affected limb appears to respond to increased metabolic demand by increasing limb blood flow.

Coarctation in the first year of life. Patterns of postoperative effect.

From 1975 to 1982, 31 infants were operated upon in the first year of life for aortic coarctation and congestive heart failure. Operations performed were resection and end-to-end anastomosis (RETE) in 14, subclavian flap aortoplasty (SFA) in six, patch aortoplasty (PA) in five, and other procedures in six. Thirty of the thirty-one (97%) survived the operation. To assess the effect of operation, 26 infants were studied noninvasively with Doppler arm-to-leg pressure measurements at rest and with stress. Preoperatively, the median arm-to-leg gradient at rest was 77 mm Hg. Serial postoperative Doppler studies demonstrated progressive changes in arm-to-leg pressure gradients: 69% had residual arm-to-leg gradients that spontaneously resolved, 13% had residual gradients that persisted, 13% had progressive increase in gradient, and one child had neither early nor late gradient. Stress testing often unmasked gradients not present in the resting state. No differences were noted among the three surgical groups: RETE, SFA, and PA. From our experience, we have made four conclusions with regard to repair of coarctation of the aorta in infants. First, surgical survival is expected. Second, the effect of the operation is dynamic, with four patterns defined: (1) complete relief of coarctation, (2) transient residual coarctation, (3) persistent residual coarctation, and (4) recurrent coarctation. Third, optimal surgical therapy seems to be an eclectic approach. Fourth, physiological evaluation of coarctation in infants can be obtained by Doppler techniques in conjunction with stress testing.

Relative inotropic and chronotropic activity of beta-adrenoceptor stimulants in anaesthetised, areflexic dogs.

The use of different methods of measuring contractility and the effects of cardiovascular reflexes are among the factors which complicate the assessment of selective inotropic activity of beta-adrenoceptor agonists. The effects of dobutamine, prenalterol, noradrenaline and isoprenaline on heart rate, iliac blood flow, left ventricular pressure, max dP/dt and (dP/dt) divided by IIT (integrated isometric tension) were evaluated in anaesthetised dogs in which the hearts were denervated and blood pressure held constant. All the drugs caused dose-dependent increases in heart rate and contractility. The relative chronotropic and inotropic activity of each agonist was evaluated. At most doses studied the agonists exerted similar chronotropic and inotropic activity when compared to the non-selective agonist isoprenaline. It is likely that the inotropic selectivity observed with prenalterol and dobutamine in previous studies depends on factors other than direct drug action.

Inotropic selectivity of salbutamol and terbutaline in anaesthetised, areflexic dogs.

The cardiovascular effects of the selective beta 2-adrenoceptor agonists salbutamol and terbutaline have been evaluated in anaesthetised, areflexic dogs. The preparation was designed to reduce the effects of changes in cardiac function mediated via reflex responses to changes in blood pressure. The effects of the selective beta 2-adrenoceptor agonists on heart rate, hindlimb blood flow, left ventricular pressure, max dP/dt and (dP/dt)/IIT (integrated isometric tension) were compared to those of isoprenaline, while blood pressure was held constant. All three drugs produced dose-dependent increases in heart rate, myocardial contractility and iliac blood flow. When equiactive inotropic doses of isoprenaline and salbutamol were compared, salbutamol produced a significantly lower chronotropic effect. A similar inotropic selectivity was found when terbutaline was compared to isoprenaline. beta 2-Adrenoceptor blockade abolished this selectivity. It is concluded that, in the absence of autonomic reflex activity, the beta 2-selective adrenoceptor agonists are relatively selective inotropic stimulants.

Pulque intake during pregnancy and lactation in rural Mexico: alcohol and child growth from 1 to 57 months.

OBJECTIVE: To examine maternal intake of a mildly alcoholic beverage (pulque) during pregnancy and lactation, and its potential effect on postpartum child growth and attained size. DESIGN: A prospective cohort study that followed mothers (during pregnancy and lactation) and their offspring (from birth to approximately 57 months of age). SETTING: Six villages in rural, central Mexico. SUBJECTS: Subjects are 58 mother-child pairs. Pulque intake was measured as part of a dietary assessment that was conducted for 2days/month during pregnancy and early lactation. RESULTS: Most mothers consumed pulque during pregnancy (69.0%) and lactation (72.4%). Among pulque drinkers, the average ethanol intake was 125.1 g/week during pregnancy and 113.8 g/week during lactation. Greater pulque intake during lactation, independent of intake during pregnancy, was associated with slower weight and linear growth from 1 to 57 months, and smaller attained size at 57 months. Low-to-moderate pulque intake during pregnancy, in comparison to either nonconsumption or heavy intake, was also associated with greater stature at 57 months. CONCLUSIONS: Pulque intake during lactation may have adversely influenced postnatal growth in this population. Public health interventions are urgently needed in Mexico to reduce heavy intake of pulque by pregnant and lactating women, and to replace intake with foods that provide the vitamins and minerals present in the traditional alcoholic beverage.

The chronological distribution of enamel hypoplasia in human permanent incisor and canine teeth.

The frequencies and chronology, based on a standard tooth development chart, of enamel hypoplasia derived from permanent upper central incisors and mandibular canines were compared for 42 prehistoric Amerindians. Between 0.5 and 4.5 years, when the crowns of both these teeth are developing, hypoplasias were 1.36 times more common on the incisors (54 hypoplasias/incisor; 40 hypoplasias/canine). Hypoplasias on incisors occurred earlier (mean = 2.50; median at 2.0-2.5 years) compared to the canine (mean = 3.51; median at 3.5-4.0 years). Differences in published frequencies and chronologies of hypoplasias may be explained, in part, by an indefinable variation in the teeth studied. The highest density of hypoplasias on both tooth crowns was just cervical to the midpoint, suggesting that developmental rates and crown geometry may influence the ability of the crown to record stressful events.

Infestation in the dog by the paralysis tick, Ixodes holocyclus. 4. Cardiovascular effects.

To determine the extent and significance of changes in heart rate and rhythm noticed previously in dogs paralysed with Ixodes holocyclus, two studies were undertaken. In one the electrocardiogram was recorded at stages throughout the disease and the traces analysed for changes, while in the second a detailed study of the effect of Ixodes holocyclus on the cardiovascular system was undertaken. The electrocardiographic changes were extremely variable between stages and between dogs. Generally, if a dysrhythmia occurred in stages 1, 2 or 3 it tended to be sinus tachycardia, ventricular tachycardia or sinus arrest. In stage 4 sinus arrest, sinus bradycardia, or sinus or ventricular tachycardia were the prominent dysrhythmias, whereas in stage 5 sinus bradycardia predominated. Cardiovascular measurements indicated an increase in peripheral vascular resistance leading to a significant elevation in mean arterial pressure at all stages of the disease. Cardiac output was decreased significantly only at stage 2, although it was below the control measurements at all stages. Pulmonary arterial pressure was significantly elevated at stages 2, 3 and 4 due most probably to an increase in pulmonary vascular resistance. Myocardial contractility was not significantly changed throughout the disease. The changes observed in the electrocardiogram and the cardiovascular system in stages 1, 2 and 3 are unlikely to be due to hypoxia and could represent dysfunction of the autonomic nervous system. During stages 4 and 5 oxygen levels were below normal and the bradycardia seen terminally is almost certainly due to hypoxaemia.(ABSTRACT TRUNCATED AT 250 WORDS)